Mortality Studies "C"

August 3, 2004:

The Dow mortality studies mentioned in this section were temporarily unavailable on a Dow web site.  The studies are once again available but on a different site.  If problems are encountered with any links, please inform Dioxinspin.com via "Contact".

Dow’s Dioxin Data website contains two epidemiology studies that studied more than 35,000 male Dow employees and followed their mortality for more than fifty years. Although the 2,000 or so Midland plant employees exposed to dioxins were included in the 35,000 studied employees, these two studies were not dioxin specific but, rather, compared the mortality of employees exposed to a wide range of chemicals. Unfortunately, the two large studies did not define the type or the extent of chemical exposure experienced by the workers.

The first Study, GG Bond, et al, 1987 evaluated the mortality of 37,682 Dow employees that worked for Dow at the Midland and Bay City sites from 1940 to 1982. The second study, CJ Burns, et al, 2002 evaluated the mortality experience of 42,076 male employees and 11,706 female employees at the same sites from 1940 to 1994.   Although Burn, 2002 does state that the purpose of the subsequent study is to “follow the Midland and Bay City workforce an additional twelve years”, the study is not really an update of the original 1940 to 1982 study.   Due to the large number of changes made in the composition of the studied cohort, it is very difficult to compare Bond, 1987 and Burns, 2002.

The two studies are particularly important for they demonstrate a number of ways that cohort composition and cohort characteristics can be manipulated to affect the mortality calculations and thus affect the findings and conclusions of an epidemiology study.

However, before we examine the actual study, a short comparison of Dow's “PR summaries” versus the actual summary presented in one of the studies seems appropriate.

The Overview of Dow Worker Health Studies on Dow’s Dioxin Data website summarized the Bond, 1987 study in the following manner, “Cause-specific mortality was surveyed among 37,682 male employees with three or more days of service between 1940 and 1982 at two Dow facilities. Comparisons of observed mortality demonstrated lower mortality in the cohort from each of the major causes of death, including total malignant neoplasms.”

This summary about the total cohort is correct and does seem to indicate that all is “well” with this group of workers. However, a much different picture would have been given if the Overview included the very next sentence from the original abstract, “Unique among hourly employees was significant excess mortality in the categories of other lymphatic tissue.... and both hourly and salaried nonexempt employees experienced significantly higher mortality from other and ill-defined cancers”.

It’s not surprising that the Overview also did not quote other parts of the body of the Bond, 1987 report, “However, [in the case of the hourly workforce] a significant increasing trend in mortality from cancers of all sites combined was observed with increasing duration of employment, and those employed for 20 years or more experienced a significant excess relative to those employed for fewer than five years (RR = 1.9, 95% CL = 1.04-1.35).

Bond, 1987 goes on, “This [higher hourly mortality] was principally attributable to significantly increasing trends in mortality from cancers of the stomach, large intestine, prostate and lung... Cancers of the stomach, large intestine and prostate were significantly elevated among those with 20 or more years of service...”

Obviously, it would be a shame to ruin great PR spin by including details about employees dying prematurely.   If this study was “dioxin-specific”, it would certainly be classified as “DioxinSpin”. However, because the study focused on general chemical exposure and not dioxins, let’s just call the PR summary “Industrial-Strength DowSpin”.

These two studies will be discussed in greater detail in an attached document that can be accessed via the link shown below.  However, it is suggested that the reader also examine both studies (even briefly) to gain a better understanding of the type of information that is presented in the two studies.  Both Bond, 1987 and Burns, 2002 are available via the links shown below.

Several aspects of the Burns, 2002 study seem unusual and may even be significant enough to label the study as flawed and unreliable.  However, I am not an epidemiologist and, perhaps, a reader with more expertise can address what constitutes a "flawed' study.

     Link to Commentary: Bond, 1987 and Burns, 2002 Commentary

     Link to Bond, 1987: 

     Link to Burns, 2002:

These and other Dow mortality studies are found on :

http://www.dow.com/facilities/namerica/michigan/dioxin/addinfo/healthstudies.htm